1. Field of the Invention
The present disclosure relates to a heat-shrinkable tube having tearability, which is made of a fluororesin, and particularly to a tearable tube having heat-shrinkability, in which a material for the tube is composed of a thermoplastic fluororesin.
2. Background Art
Tubes having tearability have been used as a protective member until various articles came into use. Among them, tearable tubes made of a fluororesin have characteristics of the fluororesin such as heat resistance, chemical resistance, water and oil repellency, non-adherence, and self-lubricity, which may not be obtained by using tearable tubes made of a hydrocarbon-based synthetic resin. With these characteristics, the tearable tubes are used as protective tubes for precision instrument and electronic parts, or tubes for medical device introduction for introducing a catheter, a guide wire, and the like into the body, and assembly jigs such as a catheter, and when the tubes are no longer necessary, the tubes can be torn and removed. In particular, tearable tubes having heat-shrinkability enable internal articles to be securely protected, but the heat-shrinkage rate needs to be high in order to sufficiently adhere a heat-shrinkable tube to the internal articles. Further, the tubes are required to be easily torn without using a special instrument. Tearable tubes in the related art are provided with a cut on the surface in a longitudinal direction throughout the full length thereof, and are not easily torn at all.
International Publication No. WO2013/077452 suggests a tube which can be torn without requiring an excessive cut and has high heat-shrinkage rate. However, when the diameter of a tube to be needed is narrowed depending on the use, there is a problem in that the tear straightness becomes insufficient. When the diameter of the tube is narrow, it is difficult to uniformly apply force which cuts open (tears) the tube in a lateral direction to the tube. Even when tear force is non-uniformly applied, excellent tear straightness is needed in order to surely tear the tube throughout the full length thereof. In addition, when the tube is used as an assembly jig such as a catheter, high heat-shrinkability is required in addition to tear straightness, and simultaneously, since the tube affects the dimensional accuracy of a completely assembled catheter, dimensional accuracy when the tube is shrunk is required. Errors of several percentages (%) in both internal diameter and length when the tube is shrunk are significantly problematic.